1. Field of the Invention
This invention is directed to a dielectric material and method for its manufacture, for use in the transmission of electromagnetic waves. The dielectric material can also be used in a variety of applications, including, for example, various transmission media such as microstrip, strip line or coaxial lines, or as a radome to protect an antenna from exposure to the environment.
2. Description of the Related Art
From electromagnetic theory, it can be shown that a coaxial transmission line of length L has a phase length given by the following equation: ##EQU1## where .psi. is the electrical or phase length of the dielectric material used in the transmission line (in radians), L is the length of the transmission line (in meters), .lambda. is the wavelength of the electromagnetic wave transmitted on the line (in meters), .epsilon. is the relative dielectric constant of the transmission line (a dimensionless quantity), f is the frequency of the electromagnetic wave transmitted in the dielectric material (in Hertz), and c is the velocity of light (in meters per second). The relative permittivity of common dielectrics used in industry is approximately constant over the frequency range of devices or components constructed from such materials. Accordingly, as indicated by equation (1), the electrical length .psi. of the coaxial transmission line increases with the operating frequency, a phenomenon that leads to undesirable effects in many applications. For example, the increase in electrical length .psi. is the cause of frequency limitations in many series-fed antenna arrays due to antenna beam steers introduced by the phase change with frequency. The increase in phase length with increasing frequency is also the cause of frequency limitations in microstrip antenna elements, filters and many other devices. It would be desirable to provide a dielectric material for use in the transmission of electromagnetic waves that does not suffer from frequency limitations due to variations in phase length with respect to frequency.